1. Field of the Invention
The invention concerns a twin-tube infrared radiator with an inner bridge that separates two housings which run in a longitudinal direction along the tube. The invention further concerns a process for manufacturing the infrared radiator.
2. Description of the Related Art
An infrared radiator is described in German utility model application DE-U1 9,113,002, in which the lamp tube is shaped as twin tubes made of quartz glass and separated by an intermediate bridge. The twin tubes extend over a length of two equal radiator sections. Each of the housings of the twin tube consists of two housing halves. A heating spiral is arranged in each one of the four housing halves.
The heating spirals of each radiator section are arranged in a series by pairs. Each heating spiral is provided with a connection wire for the electrical current supply at its first end. The electrical connections for each heating spiral pair are guided out of the twin tubes at each of the front sides of the twin tubes by means of a vacuum-sealed area crimped between two welded molybdenum sheets.
The heating spirals of each of the heating spiral pairs are interconnected via an M-shaped bent molybdenum wire. The molybdenum wire grips an end of the heating spiral and is guided back by means of a first U-shaped bend within the housing, parallel to the heating spiral up to the first end. The inner bridge is bored out or milled out over a length of some centimeters in the area of the first end of the twin tube. Between the upper edge of the crimped area and the floor of the bridge bore is a cut a few centimeters wide. The molybdenum wire extends through this cut over a second U-shaped bend into the other housing where it is connected to the second heating spiral. Viewed in both housings, the molybdenum wire is M-shaped, and a level plane runs into the inner bridge. The molybdenum wire is coated with a quartz glass capillary tube in the area of the heating spiral to avoid short circuits. The heating spirals are held centered over a length within the housing by regularly distributed gap holders.
The manufacture of the known infrared radiator is very time consuming and requires great skill. Special asymmetric gap holders are necessary so that the heating spiral is always arranged centrally within the housing, despite the molybdenum wire that runs back parallel to the heating spiral.
The heating spiral is guided with great force into the twin tube in the known infrared radiators, while the gap holders press onto the inner walls of each housing. Therefore, a strong mechanical tension is applied to the heating spiral. After a few months, it is no longer tension-free. Thus, it runs the risk of creasing during operation. Therefore, the length of the heated zone is modified. This leads to breakdowns in the known infrared radiators.
During heating of the tungsten heating spiral while in operation, the material of the spiral recrystallizes. This changes the spiral measurements. In the known infrared radiators, it is therefore necessary to recrystallize the heating spiral before mounting. However, this makes the heating spiral rough, making installation in the twin tubes even more difficult. Furthermore, the recrystallization of the heating spiral requires a lot of time and great cost.
A twin tube radiator is also known from German utility model DE-U1 9,115,621, wherein both heating spirals are interconnected via a molybdenum handle, and wherein the molybdenum handle grips each front side end of the heating spiral. For facilitating the mounting of the molybdenum handle, it is proposed to remove the inner bridge of the twin tube by milling or boring a slit into the front side. The molybdenum handle is laid into the slit formed in this manner and then the front side of the twin tube is crimped. The known process permits the processing of the twin tube and the mounting of the molybdenum handle from the open side. The molybdenum handle is easily contorted to facilitate its insertion from the open front side. This leads, however, to position modifications of the heating spirals during the insertion of the radiator.
A further short-wave infrared radiator in the form of a twin tube is described in German utility model DE-U1 8,913,683, in which an infrared radiator of double length is created by welding together two individual radiators at their ends, whereby the individual radiators are connected independently of each other and are separated by a separator wall. The connection of the heating spirals takes place in each individual radiator by means of the handle mounted in the same way as the molybdenum handle in DE-U1 9,115,621.